1. Field of the Invention
This invention relates to apparatus for hydraulic brake or clutch control, in particular for a motor vehicle, comprising at least one emitter or receiver cylinder having a piston.
More particularly, the invention relates to apparatus for hydraulic brake or clutch control for a motor vehicle, comprising at least one cylinder which includes a cylinder body having at the front a base portion and being open at the rear, a piston sliding axially in an internal bore of the cylinder body, and at least one dynamic sealing member carried by the cylinder body for cooperation with the outer periphery of the piston, wherein the cylinder body is of synthetic material such as plastics material, and wherein the piston has a front face bounding a hydraulic chamber.
2. Description of Related Art
An apparatus of that kind is described, for example, in the documents DE-U-29516488, FR-B-274920 or in French patent application No. 98 07213 of Jun. 9, 1998.
An object of the invention is to propose a control apparatus of the type mentioned above, having reduced manufacturing costs and simplifying the design of the cylinder body.
With this in view, the control apparatus in accordance with the invention is characterised in that the cylinder body includes, arranged consecutively in the axial direction from front to rear, a blind front piece which includes the said base portion, a central piece, and a rear piece which is open towards the rear, the said pieces being joined together in a sealed manner, in that the internal bore consists of a front portion and a rear portion, which are formed in the front piece and rear piece respectively of the cylinder body, and in that the said dynamic sealing member is mounted in the central piece of the cylinder body.
With such a design it is in particular possible to standardise the front and rear pieces of the cylinder body and to create a range of products by making a range of central pieces which are different from each other, in particular for the purpose of incorporating means for feeding the hydraulic chamber and means for fastening the control apparatus, which vary from one apparatus to another, especially as a function of the model and type of vehicle that it is to equip.
In accordance with further features of the invention:
the said sealed joint is an adhesively bonded joint;
the said sealed joint is a joint which is made by welding with indirect application of heat;
the said sealed joint is a joint which is made by welding with the aid of at least one energy source of the laser type;
the said sealed joint is a welded joint made by infrared radiation, for example of the laser type;
the said sealed joint is a joint made by ultrasonic welding;
the said sealed joint is a joint made by friction welding; the said sealed joint is a joint made by high frequency welding;
the said sealed joint is a welded joint made by induction welding of ferromagnetic members;
the sealed joint is obtained by mirror welding;
the piston extends through the central piece of the cylinder body with a radial clearance;
an axially oriented tubular rear portion and an axially oriented tubular front portion of the front piece and rear piece of the cylinder body, respectively, are welded to a complementary front portion and rear portion, respectively, of the central piece of the cylinder body;
the outer peripheral surface of the said tubular portion is fixed sealingly, by welding with indirect application of heat, to an internal peripheral surface of the said complementary portion of the central piece of the cylinder body;
the inner peripheral surface of the said tubular portion is fixed sealingly, by welding with indirect application of heat, to an external peripheral surface of the said complementary portion of the central piece of the cylinder body;
the said tubular portion is in axial abutment against a radial shoulder of the central piece of the cylinder body;
the central piece includes a transverse duct which is open in a substantially radial direction into an axially oriented central hole of the central piece in facing relationship with the outer periphery of the piston;
the central piece of the cylinder body is configured as a transverse plate for fastening the control apparatus;
the apparatus includes two dynamic sealing members, namely a front member and a rear member, which are mounted within the central piece of the cylinder body;
the front dynamic sealing member and the rear dynamic sealing member are each, respectively, disposed in a housing formed in the central piece of the cylinder body, which is open radially inwards;
the rear end of the rear piece of the cylinder body includes at least one abutment adapted to cooperate with a rear end of the piston so as to limit rearward axial displacement of the piston;
the piston includes a peripheral piston jacket which is fixed axially to the piston and which slides axially in the internal bore of the cylinder body;
the piston jacket has at least one hole for providing communication between the inside and the outside of the piston jacket, and the hole is adapted to be displaced to either side of a dynamic sealing member;
the piston jacket is of metal.